As computing devices have become more complex, they have also become more feature-rich. Devices such as cellular phones now contain sophisticated processors and are capable of performing such tasks as video and audio playback, electronic banking and secure information storage. Hardware, service, content and software providers all have vested interests in protecting their assets from unauthorized access or tampering. For example, a cellular phone provider may want to restrict access to certain “premium” phone features such as video or audio content. Given the large investment by such companies and the quantity and type of information stored in devices such as cellular phones, it is important to be able to prevent unauthorized copying, distribution or access to data.
There are a number of common methods used to gain unauthorized access to a computing device, including: using an improperly disabled or non-disabled test interface port such as a Joint Test Action Group (JTAG) port; purposefully operating the computing device outside its designed temperature or voltage tolerances; altering traces or adding components to the printed circuit board to which the computing device is attached; and various types of software attacks. It is possible to provide both hardware and software for detecting and mitigating the effects of these and other types of attacks. It is advantageous to be able to differentiate between types of attacks to allow different responses by a system with which the computing device communicates. It is also advantageous to be able to provide notice that a device has been the subject of an attack without alerting the attacker to the fact that the attack has been detected.